I've seen this play out in several churches. It is very sad and very confusing. Yet, those who are embroiled in it always manage to put a spiritual twist to what they say and why they are doing what they are doing.
If something is wrong Biblically in a church, we should try to make it right by talking to the pastor and leaders or whoever we think is in the wrong. We should never go around stirring up other people to gain a following. If going privately to them doesn't solve anything, then do according to Matthew 18 and take a couple of others with you to talk to them. Only if this does not solve the problem should you bring it before the church. And I don't believe bringing it before the church means you go around talking to others behind the person's back to try and gain a following. Bringing it before the church means you call a meeting of the church members and you stand up and tell them what the issue is.
In most cases I would venture a guess that people wouldn't want to do these steps because they know their complaint is full of bitter envey and self-seeking and they don't want to sully their own reputation in front of the whole church.
The best thing a person can do who is unhappy and can't exist peacefully in the church is to leave quietly. There will be those that will approach them for why they left and they will hear the complaint. If they are wise they will go and speak to those accused and try to find out both sides of the story before making up their minds and they will not spread what they hear around.
I can't say I have always followed these guidelines. In cases where I have not, I wish I had. In other cases I have stood back and observed what was going on and stayed out of the fray.